/*
 * OutputNode.java July 2006
 *
 * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.stream;

/**
 * The <code>OutputNode</code> object is used to represent a cursor
 * which can be used to write XML elements and attributes. Each of
 * the output node objects represents a element, and can be used
 * to add attributes to that element as well as child elements.
 *
 * @author Niall Gallagher
 */
public interface OutputNode extends Node {

    /**
     * This method is used to determine if this node is the root
     * node for the XML document. The root node is the first node
     * in the document and has no sibling nodes. This is false
     * if the node has a parent node or a sibling node.
     *
     * @return true if this is the root node within the document
     */
    boolean isRoot();

    /**
     * This returns a <code>NodeMap</code> which can be used to add
     * nodes to the element before that element has been committed.
     * Nodes can be removed or added to the map and will appear as
     * attributes on the written element when it is committed.
     *
     * @return returns the node map used to manipulate attributes
     */
    NodeMap<OutputNode> getAttributes();

    /**
     * The <code>Mode</code> is used to indicate the output mode
     * of this node. Three modes are possible, each determines
     * how a value, if specified, is written to the resulting XML
     * document. This is determined by the <code>setData</code>
     * method which will set the output to be CDATA or escaped,
     * if neither is specified the mode is inherited.
     *
     * @return this returns the mode of this output node object
     */
    Mode getMode();

    /**
     * This is used to set the output mode of this node to either
     * be CDATA, escaped, or inherited. If the mode is set to data
     * then any value specified will be written in a CDATA block,
     * if this is set to escaped values are escaped. If however
     * this method is set to inherited then the mode is inherited
     * from the parent node.
     *
     * @param mode this is the output mode to set the node to
     */
    void setMode(Mode mode);

    /**
     * This is used to set the output mode of this node to either
     * be CDATA or escaped. If this is set to true the any value
     * specified will be written in a CDATA block, if this is set
     * to false the values is escaped. If however this method is
     * never invoked then the mode is inherited from the parent.
     *
     * @param data if true the value is written as a CDATA block
     */
    void setData(boolean data);

    /**
     * This is used to acquire the prefix for this output node. If
     * the output node is an element then this will search its parent
     * nodes until the prefix that is currently in scope is found.
     * If however this node is an attribute then the hierarchy of
     * nodes is not searched as attributes to not inherit namespaces.
     *
     * @return this returns the prefix associated with this node
     */
    String getPrefix();

    /**
     * This is used to acquire the prefix for this output node. If
     * the output node is an element then this will search its parent
     * nodes until the prefix that is currently in scope is found.
     * If however this node is an attribute then the hierarchy of
     * nodes is not searched as attributes to not inherit namespaces.
     *
     * @param inherit if there is no explicit prefix then inherit
     * @return this returns the prefix associated with this node
     */
    String getPrefix(boolean inherit);

    /**
     * This is used to acquire the namespace URI reference associated
     * with this node. Although it is recommended that the namespace
     * reference is a URI it does not have to be, it can be any unique
     * identifier that can be used to distinguish the qualified names.
     *
     * @return this returns the namespace URI reference for this
     */
    String getReference();

    /**
     * This is used to set the reference for the node. Setting the
     * reference implies that the node is a qualified node within the
     * XML document. Both elements and attributes can be qualified.
     * Depending on the prefix set on this node or, failing that, any
     * parent node for the reference, the element will appear in the
     * XML document with that string prefixed to the node name.
     *
     * @param reference this is used to set the reference for the node
     */
    void setReference(String reference);

    /**
     * This returns the <code>NamespaceMap</code> for this node. Only
     * an element can have namespaces, so if this node represents an
     * attribute the elements namespaces will be provided when this is
     * requested. By adding a namespace it becomes in scope for the
     * current element all all child elements of that element.
     *
     * @return this returns the namespaces associated with the node
     */
    NamespaceMap getNamespaces();

    /**
     * This is used to get the text comment for the element. This can
     * be null if no comment has been set. If no comment is set on
     * the node then no comment will be written to the resulting XML.
     *
     * @return this is the comment associated with this element
     */
    String getComment();

    /**
     * This is used to set a text comment to the element. This will
     * be written just before the actual element is written. Only a
     * single comment can be set for each output node written.
     *
     * @param comment this is the comment to set on the node
     */
    void setComment(String comment);

    /**
     * This is used to set a text value to the element. This should
     * be added to the element if the element contains no child
     * elements. If the value cannot be added an exception is thrown.
     *
     * @param value this is the text value to add to this element
     * @throws Exception thrown if the text value cannot be added
     */
    void setValue(String value);

    /**
     * This is used to change the name of an output node. This will
     * only affect the name of the node if the node has not yet been
     * committed. If the node is committed then this will not be
     * reflected in the resulting XML generated.
     *
     * @param name this is the name to change the node to
     */
    void setName(String name);

    /**
     * This method is used for convenience to add an attribute node
     * to the attribute <code>NodeMap</code>. The attribute added
     * can be removed from the element by using the node map.
     *
     * @param name  this is the name of the attribute to be added
     * @param value this is the value of the node to be added
     * @return this returns the node that has just been added
     */
    OutputNode setAttribute(String name, String value);

    /**
     * This is used to acquire the <code>Node</code> that is the
     * parent of this node. This will return the node that is
     * the direct parent of this node and allows for siblings to
     * make use of nodes with their parents if required.
     *
     * @return this returns the parent node for this node
     */
    @Override
    OutputNode getParent();

    /**
     * This is used to create a child element within the element that
     * this object represents. When a new child is created with this
     * method then the previous child is committed to the document.
     * The created <code>OutputNode</code> object can be used to add
     * attributes to the child element as well as other elements.
     *
     * @param name this is the name of the child element to create
     */
    OutputNode getChild(String name) throws Exception;

    /**
     * This is used to remove any uncommitted changes. Removal of an
     * output node can only be done if it has no siblings and has
     * not yet been committed. If the node is committed then this
     * will throw an exception to indicate that it cannot be removed.
     *
     * @throws Exception thrown if the node cannot be removed
     */
    void remove() throws Exception;

    /**
     * The <code>commit</code> method is used flush and commit any
     * child nodes that have been created by this node. This allows
     * the output to be completed when building of the XML document
     * has been completed. If output fails an exception is thrown.
     *
     * @throws Exception thrown if the node cannot be committed
     */
    void commit() throws Exception;

    /**
     * This is used to determine whether the node has been committed.
     * If the node has been committed, then this will return true.
     * When committed the node can no longer produce chile nodes.
     *
     * @return true if this node has already been committed
     */
    boolean isCommitted();
}
